The invention is in the field of electronic reproduction technology and is directed to a device for pixel-by-pixel and line-by-line, optoelectronic scanning of masters chucked on a scanner drum. Such a scanner drum device, referred to as a drum scanner below, can be designed for scanning black-and-white or chromatic masters in reflected light and/or transmitted light.
A drum scanner for scanning transparency masters is composed, for example, of a rotating, transparent scanner drum onto which a transparency master to be scanned is chucked, of a light source for pixel-by-pixel illumination of the transparency master and of a scanner element having a scanner objective, a scanner diaphragm and an optoelectronic transducer for converting the scan light the transparency master allows to pass into an image signal, which represents the luminance values of the scanned picture elements.
The light required for the pixel-by-pixel illumination of the transparency master is transported, for example, from a light source located outside the scanner drum through a light conductor into the hollow-cylindrical interior of the scanner drum and is imaged thereat onto the transparency master as an illumination spot with a matching objective and a deflection mirror. The scan light modulated with the image content of the transparency master proceeds through the scanner objective into the scanner element located outside the scanner drum and is converted thereat into an image signal by optoelectronic conversion.
The scanner element on the one hand and the optical elements on the other hand are respectively secured to an arm of a U-shaped feed support, whereby the arm carrying the optical elements projects into the scanner drum at the end face.
For planar scanning of the transparency master, the feed support moves in the axial direction of the rotating scanner drum.
In order to be able to scan masters having different formats, the standard scope of a drum scanner comprises scanner drums having different diameters that are chucked in the drum scanner dependent on the format of the master to be scanned. In this case, lens systems must be manually replaced at the feed support for optimum setting of the size of the illumination spot on the transparency master in order to compensate the different radial distances between the central arm of the feed support and the generated surface of the respective scanner drum. For optimum focusing of the luminance-modulated scan light coming from the transparency master onto the scanner diaphragm, the scanner element is equipped with interchangeable lenses that must be manually pivoted into the beam path dependent on the diameter of the scanner drum employed. The employment of such sets of lenses and interchangeable objectives is relatively complicated.
It is therefore an object of the invention to improve a device for pixel-by-pixel and line-by-line, optoelectronic scanning of transparency and opaque masters chucked on scanner drums such that optical adaptations, particularly given employment of scanner drums having different diameters, can be implemented in a simple way and automatically to the farthest-reaching extent.
According to the apparatus of the invention for point-by-point and line-by-line opto-electronic scanning of a master, a scanner drum is provided for chucking a master to be scanned. An illumination unit is provided for the master. A scanner objective is provided, and a scanner element converts the scan light modulated with the content of the master and then the scan light is focused with the scanner objective into an image signal. A feed support is provided in which the scanner objective in the scanner element are arranged, the feed support executing a feed motion in the direction of a rotational axis of the scanner drum for scanning of the master. The scanner comprises a reflected light illumination for generating an illumination spot on an opaque master. The scanner objective corrects focusing of the scan light onto the scan element given employment of scanner drums having different diameters and is seated displaceable into a radial working position on an optical axis of the scanner element determined by a diameter of the respective scanner drum. Reflective light illumination is displaceably arranged for optimizing the illumination spot given employment of scanner drums having different diameters.
The invention is explained in greater detail below with reference to FIGS. 1 through 5.